Stabilization of polymers with uv stabilizers and antioxidants



United States Patent ice 3,445,424

Patented May 20, 1969 3 445 424 incorporating therewith a small amounteach of a stabilizer against ultraviolet light and an antioxidant. Also,STABILIZATION 0F POLYMERS WITH UV according to the invention,compositions of these addi- STABILIZERS AND ANTIOXIDANTS fives atrovided Robert J. Martinovich, Bartlesville, Okla., assignor e p toPhillips Petroleum Company, a corporation of 5 DESCRIPTION OF THEPREFERRED Delaware No Drawing. Continuation-impart of application Ser.No. EMBODIMENTS 207,017, July 2, 1962. This application Dec. 18, 1967,The polyolefins of polymers of copolymers to which Ser. No. 691,139

the invention is applicable include those which can be Us Cl gl g 45/5829/04 29/02 2 Claims 10 prepared from aliphatic l-olefins having from 2to 8 carbon atoms per molecule and no branching nearer the double bondthan the 4-position at a polymerization tem- ABSTRACT OF THE DISCLOSUREperature of up to about 500 F. with a catalyst active for suchpolymerization and comprising chromium oxide upon a suitable carrier, atleast a part of the chromium being in the hexavalent state when thehydrocarbon contacts the catalyst at the initial contacting of thecatalyst with the hydrocarbon.

Other polymers and copolymers, including solid polymers and copolymers,of l-olefins prepared by other known methods can also be stabilizedaccording to the present invention, which will now be described asapplied to a solid polymer of ethylene and a solid copolymer of A solidpolymer of an aliphatic l-monoolefin is stabilized against weathering byincorporating an antioxidant such as, for instance,dilaurylthiodipropionate or 4,4- thiobis(3-methyl-6-t-butyl phenol), anda UV stabilizer such as, for instance, 2-hydroxy-4-n-octoxybenzophenone,into the polymer.

CROSS REFERENCE TO RELATED INVENTIONS This is a continuation-in-part ofmy copending appliy and l-blltonocation Ser. No. 207,017, filed July 2,1962, now Patent It W111 be understood y one skllled m the art n Number3,370,036 issued Sept. 28, 1967. possession of this disclosure and thegeneral knowledge g of the art relating to the ultraviolet or oxidativedeg- BACKGRO'UND OF INVENTION radation of polyolefins such aspolyethylene, polypropyl- This invention relates to the stabilization ofa polymer. ene, etc., and copolymers as herein discussed, that the Itrelates to the stabilization against ultraviolet radiation results whichare herein exemplified by data obtained or oxidative or heat degradationof a polymer, for exwith the herein identified polyolefin (polyethylene)and ample a l-olefin polymer or a copolymer of a l-olefin copolymer(ethylene and l-butene copolymer) can also with a higher molecularweight l-olefin, e.g., a copolymer be obtained with other relatedpolymers or copolymers. of ethylene and l-butene. Polymer '(A) inExamples 1 through 4 was poly- NVE ethylene. Polymer (B) in Example 5was a copolymer SUMMARY OF THE I NTION of ethylene and butene-l. Thispolymer contained about It is an object of this invention to stabilize apolymer to 2.5 percent butene-l. The polymer and copolymer are preserveits desirable properties such as tensile strength, characterized by thefollowing properties:

Property: Polymer (A) Polymer (B) Test Method Density- 0.960 gmsJce0.950 gins/co ASTM D1505-57T. Melt Index 0.2 1.2 ASTM D1238-57T. TensileStrength. 4,400 p.s.i H 3,800 p.s.i ASTM D638-58T. Elongation 30percent. pereen ASTM D63858T. Environmental Stress: Cracking Resistance60 hours 55 hours ASTM D1693-59'l.

etc. It is another object of this invention to stabilize a Example I$231232? that, amazes; e higher molecular weight l-olefin. It is afurther object fives were mcorpomted as herem descnbed: of thisinvention to stabilize against ultraviolet degradasantonox (MonsantoChemical Company), antioxidanttion a solid polymer or copolymer of al-olefin. It is a 4,4'th1obis- (3-methyl-6-t-butyl phenol) furtherobject of this invention to provide a method for TBS (Dow ChemicalCompany), UV stabilizerparathe stabilization of a polymer or copolymersuch as polytertlary-butyl phenyl salicylate olefin or copolymerlzedolefins obtamed by polymerlzlng Weathep Tensile Elm or copolymerlzmgl-olefins as herein descrlbed. It is a Sa'mple Ometer, Strength, gationstill further object of this invention to provide a com- RunAddlfivoipefcent hours pp nt position of additives suitable for additionto a polymer or a copolymer for stabilizing the same against ultra- 5002,080 800 1,870 2.5 violet degradation, oxldatlve or heat deteriorationand 1, 250 1, 560 3.0 5 0. TBS 2,000 1,993 4.0

ggpg ig ig deslrable propemes of thfi polymer or 6 0.10 Santonox-0.50TBS3,500 3,670 14,0 Other objects and the several advantages of the in- Thecontrol prior to exposure in the Weather-Ometer vention are apparentfrom a study of this disclosure and had a tensile strength of 4400.After 200 hours exposure the appended claims. the tensile strength, asshown in the table, had been re- According to the invention, the tensilestrength of a duced to 2330. Elongation was 4 percent for this sample.polymer such as a solid polymer of a l-olefin, e.g. poly- Whereas after500 hours with 0.1 percent 4,4-thiobisethylene, polypropylene, etc., ora copolymer of say (3-methyl-6-t-butyl phenol) and 0.5 percent ofparaterethylene and a higher l-olefin, as prepared by methodstiary-butyl phenyl salicylate, after 2000 hours exposure, known in theart, for example, as disclosed and claimed the tensile strengths were,for additional polyethylene in Patent 2,825,721, issued Mar. 4, 1958,John Paul compounded, as stated, 2080 and 1993, respectively, a Hoganand Robert L. Banks, is markedly preserved by sample of thepolyethylene, here identified, including a combination of the additivesin the recited percentages, namely 0.1 percent of the former and 0.5percent of the latter, having been exposed for 3500 hours, gave atensile strength of 3670. The elongations for the three samples herediscussed, namely samples 2, 5 and 6, respectively, were 4, 4 and 14,respectively.

Thus when both additives were added according to the invention, incombination, a 3 /2 fold increase in elongation was obtained and thetensile strength was about 55 percent greater than that of the controlrun, Run 1, and this after testing for 17 times as long as the testingin the control run, i.e., testing for 3500 hours in Run 6 as againstonly 200 hours in Run 1.

It is evident from the foregoing table and its discussion that the useof the combination of the two additives to stabilize a polyolefin suchas polyethylene yields unexpectedly very greatly improved results. Theseresults could not have been foreseen. When it is borne in mind that theadditives employed are each of them considered to be very good productsfor increasing resistance to ultraviolet light and other degradationupon exposure, it will be recognized that the improvement heredemonstrated is quite out of the ordinary.

In the following are given additional examples of the invention. Similardiscussion to that of Example I can be made in regard to said examples.

Example II-A UV 531 (American Cyanamid Co.), UV stabilizer2-hydroxy-4-n-octoxybenzophenone DLTDP (American Cyanamid Co.),antioxidant-Dilaurylthiodipropionate P O LYME R (A) Weather- TensileElon- Sample Ometer, Strength, gation,

Run Additive, percent hours p.s.i. percent LTDP 500 2, 000 5. 0

4 O.%53PLTDP-O.25 UV 2, 500 4, 400 15.0

Example II-B Base polymerldentical Polymer B except melt index was 0.3.

Weather- Tensile Elon- Sample Ometer, Strength, gation,

Additive, percent hours p.s.i. percent Control 1 0.3 UV 531 0 3, 650 82Control 2.-- 0.3 DLTDP 0 3, 700 143 Run 1 0.25 UV 531-005 0 3, 650 75DLTDP.

Control 3..- 0.3 UV 531.--- 500 4, 000 30 Control 4--. 0.3 DLTDP 500 3,650 17 Run 2 0.25 UV 531-005 500 3, 950 83 DLTDP.

Control 5--- 0.3 UV 531 1, 000 3, 450 28 Control 6 0.3 DLTDP 1,000 490 3Run 3 0.25 UV 531-005 1, 000 3, 950 38 DLTDP.

Dow Chemical Co., UV stabilizer-bis-phenol-A-disalicylate Dow ChemicalCo., antioxidant-4,4-isopropylindenebis-Z-tertiary butyl phenol POLYMER(A) We ather- Tensile Elon- Sagmple Ometer, Strength, gation,

Run Additive, percent hours p.s.i. percent 3 0.50 Stabilizer-0.1 Anti-3, 000 3, 270 14.00

oxidant.

4 Example IV Santonox (Monsanto Chemical Co.), anti0xidant4,4'-

thiobis-(3-methyl-6-t-butyl phenol) OPS (Eastman Chemical Co.), UVstabilizer-p-octylphenyl salicylate Santonox (Monsanto Chemical Co.),antioxidant4,4'-

thiobis-(3-methyl-6-t-butyl phenol) UV 531 (American Cyanamid Co.), UVstabilizer-2- hydroxy-4-n-octoxybenzophenone POLYMER (B) Weather-Tensile Elon- Samp Ometer, Strength, gation, Run Additive, percent hoursp.s.i. percent 1-- Control 200 2, 000 6. 0 500 2, 000 5. 0

It appears that when both an ultraviolet stabilizer and an antioxidantare incorporated into a polymer or copolymer, here discussed, a morethan additive effect occurs and that, indeed, the tensile strength ofthe compounded materials is very considerably improved.

The polyolefins to which this invention is particularly applicable, withresults similar to those herein set forth, are the polymers andcopolymers especially solid polymers and copolymers, of ethylene,propylene, butene-l, pentene-l, hexene-l, heptene-l, and octene-l.

The combination of additives can be blended into the polymers by knownmethods, for example by simply melting the polymer or sufficientlysoftening the same so that the additives can be mechanically blendedthereinto, either as such or dissolved in a suitable solvent which thencan be recovered from the blend. Also, the additives can be blended intothe polymers during a stage of recovery from the process of theirpreparation. In the obtaining of the above data the additives wereincorporated as follows. Samples were mill blended. Dry polymer wasplaced on a two-roll mill and milled until molten, then additives wereadded and milling continued for a total time of ten minutes. Temperatureof milling was between 300350' F.

Generally, according to the invention, the amount of the antioxidant,for example, 4,4'-thiobis-(3-methyl-6-tbutyl phenol), incorporated withthe ultraviolet stabilizer, for example, paratertiary-butyl phenylsalicylate, into the polymer or copolymer to be improved with respect toits tensile strength or stability characteristics will be in the rangeof 0.05 to 0.1 percent while the amount of the latter will be 0.25 toabout 0.9 or 1, preferably about 0.5, percent by weight of the polymerto be stabilized. Further, the ratio of the latter aditive to the formerin the combination of the additives in the polymer will usually lie inthe range 2.5 to 1 to 10 to 1.

The compounds which are combined in the present invention to stabilizethe polymers or copolymers to permit the compounding of polymers whichexhibit a Weather- Ometer life period which is considerably larger thanwould be expected from the life period obtained by adding the eifects ofeach of the compounds used in the same amounts singly with the polymersor copolymers are generally available and known in the art asultraviolet stabilizers and antioxidants.

The following compounds, which are now preferred, can be used as in theexamples.

TAB LE Ultraviolet Light Stabilizers Antioxidants TBS (Dow Chemical Co.)

paratertiary-butyl phenyl salicylate.

UV 531 (American Cyanamid Santonox (Monsanto Chemical Co.)4,4'thiobis-(S-methyl-G-tbutyl phenol).

DLTDP (American Cyanamid C0.) Dilaurylthlo- LV 314 (American CyanarnidC0.) 2,2-dihydroXy-4-moctoxy benzophenone.

The polyethylene and copolymers used in the foregoing tests aregenerally available under the trademark Marlex, which is the PhillipsPetroleum Companys trademark for polyolefins produced by the so-calledlow pressure process, as now known in the art. The polymer of EX- ampleII-B contained no pigment. The polymer of Run 5, Example V, contained 2percent No. 1409 cadmium orange pigment. All of the other samplescontained 1 per cent cadmium orange pigment. The tests were carried outby aging in an Atlas Weather-Ometer.

It will be evident to one skilled in the art that according to thisinvention there is also provided a combination of additives, asdisclosed, suitable for incorporation and coaction in similar or relatedpolymeric substances.

Reasonable variation and modification are possible within the scope ofthe foregoing disclosure and the appended claims to the invention.

I claim:

1. A solid polymer of an aliphatic mono-l-olefin having a maximum of 8carbon atoms and no branching nearer the double bond than the 4-positionstabilized with a stabilizer combination comprising 0.25 to 0.9 weightpercent based on the weight of said polymer of Z-hydroxy-4-n-octoxybenzophenone and from 0.05 to 0.1 weight percent based on theweight of said polymer of dilaurylthiodipropionate.

2. A composition according to claim 1 wherein said polymer is selectedfrom the group consisting of polyethylene and ethylene-butene-l'copolymer.

References Cited UNITED STATES PATENTS 3,000,857 9/1961 Craven 260-45953,006,959 10/ 1961 Armitage et a1 26045.95 3,098,842 7/1963 Armitage eta1. 26045.95 3,322,705 5/ 1967 Kauder et al 260-4595 2,972,597 2/1961Newland 26045.85 3,144,422 8/ 1964 Homberg 26045.85 2,956,982 10/1960McCall et a1. 260-45.85

DONALD E. CZAIA, Primary Examiner.

H. E. TAYLOR, JR., Assistant Examiner.

US. Cl. X.R. 260-41,45.95

